Dipole radiators have been disclosed, for example, by the prior publications DE 197 22 742 A and DE 196 27 015 A. Dipole radiators of this type can have a common dipole structure or can consist, for example, of a crossed dipole or a dipole square, etc.
What is known as a vector dipole is disclosed, for example, by the prior publication WO 00/39894 A1. The structure of said dipole appears to be comparable to a dipole square. Due to the specific construction of the dipole radiator according to this prior publication and the special feed-in, however, this dipole radiator operates similarly to a crossed dipole which radiates in two polarisation planes oriented perpendicularly to one another. From a design standpoint, however, it is rather formed in the shape of a square, in particular due to the design of the outer contour thereof.
WO 2004/100315 A1 disclosed a further design of the aforementioned vector dipole in which the faces of each radiator half of a polarisation can be closed to a large extent over the whole surface.
Dipole radiators of this type are typically fed in such a way that one dipole half or radiator half is connected with regard to d.c. current (that is to say galvanically) to an outer conductor, whereas the inner conductor of a coaxial connection cable is connected with regard to d.c. current (thus also galvanically) to the second dipole half or radiator half. In this case, the feed-in takes place at the end regions of the dipole halves or radiator halves that face one another.
From WO 2005/060049 A1, it is known to carry out an outer conductor feed by means of a capacitive outer conductor coupling. For this purpose, the respectively associated halves of the supporting device of the antenna element arrangement can be galvanically connected to earth or capacitively coupled to earth at the foot region or at the base of the supporting device.
From CN 203386887 U, a dipole-shaped antenna element arrangement is known which comprises two pairs of radiator halves which are arranged so as to be rotated by 90° with respect to one another, so that the dipole-shaped antenna element arrangement radiates in two polarisation planes which are arranged perpendicularly to one another. Furthermore, a passive beam-shaping frame is disclosed which is arranged in parallel with the radiator halves at a distance therefrom in the direction of the reflector. Additionally, a director is disclosed which is arranged in parallel with the radiator halves, the radiator halves being arranged closer to the reflector than the director.
A disadvantage of the antenna element arrangements from the prior art is that the antenna element arrangements have too small a bandwidth for some uses.
The example non-limiting technology herein provides a dipole-shaped antenna element arrangement which can be used in mobile communication antennae and which has a bandwidth that is greater than in the antenna element arrangements known from the prior art.
This is achieved by means of the dipole-shaped antenna element arrangement is described herein. Developments of the dipole-shaped antenna element arrangement are indicated in the detailed description.
The dipole-shaped antenna element arrangement comprises two pairs of radiator halves which are arranged so as to be rotated by 90° with respect to one another, so that the dipole-shaped antenna element arrangement transmits and/or receives in two polarisation planes which are arranged perpendicularly to one another. Two radiator halves, which in this case form a pair, are arranged diagonally to one another. The radiator halves can be arranged or are arranged in a radiator plane at a distance in front of a reflector and in parallel therewith. A balancing and/or support arrangement comprising a first end and a base at a second end, which is opposite the first end, is used to hold the two radiator halves, said halves being arranged at the first end of the balancing and/or support arrangement. The base of the balancing and/or support arrangement can be fastened to a base body. Said base body is, for example, a circuit board or the reflector wherein, by means of the circuit board, preferably at least an indirect fastening to the reflector takes place. In order to increase the bandwidth, a passive beam-shaping frame is provided which is arranged towards the base at a distance from the radiator halves. The passive beam-shaping frame consists of a plurality of frame sides which form a peripheral frame web which defines an opening. The passive beam-shaping frame is oriented in parallel with the radiator plane. The passive beam-shaping frame has, in the region of the corners thereof, a broadening of the peripheral frame web thereof, said broadening of the frame web extending in parallel with the radiator plane and/or transversely to the radiator plane. By means of this forming of the passive beam-shaping frame, in contrast to the beam-shaping frames known from the prior art, the bandwidth can be appreciably increased. In particular, the reflection factor of the dipole-shaped antenna element arrangement improves in the lower frequency range. A dipole-shaped antenna element arrangement of this type can therefore be used, in particular, in the frequency range from approximately 550 MHz to approximately 960 MHz. The dipole-shaped antenna element arrangement can also be used for other frequency ranges which lie above or below this.
According to a preferred embodiment, the broadenings of the frame web extend on the inner peripheral wall thereof so that, in the region of the corners thereof, the frame web extends closer towards a longitudinal axis through the dipole-shaped antenna element arrangement. It is also possible that, alternatively or additionally thereto, the broadenings of the frame web extend on the outer peripheral wall thereof.
In another development, in a plan view of the dipole-shaped antenna element arrangement, at least part of the radiator halves overlap at least in part or in full with the broadenings of the frame web which are formed on the inner peripheral wall thereof.
The broadenings preferably occur in a tapered manner, that is to say, extending discontinuously in one or more steps. It is also possible for the broadenings to occur continuously.
In a preferred embodiment, the outer peripheral wall of the frame web is bevelled in the region of the corners thereof, wherein at said bevel, the broadening is formed transversely to the radiator plane. The broadening can extend either transversely to the radiator plane towards the base of the antenna element arrangement or in the direction of the radiator plane. The broadening preferably extends perpendicularly to the radiator plane. The corners of the outer peripheral wall of the frame web are preferably bevelled over a length which corresponds to approximately the width of the frame web at the non-broadened points thereof. The broadenings extend perpendicularly to the radiator plane, preferably over a length which also corresponds to approximately the width of the frame web at the non-broadened points thereof.
In another embodiment of the dipole-shaped antenna element arrangement, in each case two frame sides of the frame web extend towards one another forming a corner, wherein the broadenings in parallel with the radiator plane at the individual frame sides of the peripheral frame web, that is to say, those which extend towards one another forming a corner, occur over a partial length of the respective frame sides, wherein the partial lengths each extend equally far away from the corners. This results in a particularly symmetrical structure.
In a further embodiment of the dipole-shaped antenna element arrangement, a plurality or all of the frame sides of the passive beam-shaping frame each have a vane in the middle thereof, extending approximately in parallel with the radiator plane or transversely to the radiator plane. These vanes are preferably formed, in plan view, so as to be rectangular or square. They can also be trapezoid or semicircular or half-oval, and/or the edge contour can be formed so as to be n-polygonal in plan view. The vanes extend further, preferably towards the centre of the passive beam-shaping frame and, in this case, are provided on an inner peripheral wall of the frame web. It is also possible for the vanes to extend in the opposite direction, that is, outwardly. In that case, they would be arranged on an outer peripheral wall of the frame web.
In addition thereto, the bandwidth can also be increased in that a director is used, wherein the director is oriented in parallel with the radiator plane. In this case, the radiator halves are arranged or can be arranged closer to the base than the director. In this case, the outer sides of the director are rotated at an angle of between 30° and 60°, preferably 45° to the outer sides and/or inner sides of the radiator halves.
In a further embodiment of the dipole-shaped antenna element arrangement, the director comprises a recess in the centre thereof. This recess is square, wherein the inner sides of the recess of the director extend in parallel with the outer sides of the director. The director preferably comprises on each outer side a tongue protruding outwardly, that is to say, in parallel with the radiator plane. Said protruding tongue is preferably provided in the middle of each outer side of the director. By means of such a tongue, and also by means of the recess itself, the bandwidth with which the dipole-shaped antenna element arrangement can be operated can be increased.
In place of a director, in order to further increase the bandwidth, a plurality of metal strips can also be used, which are oriented in parallel with the radiator plane. In this case, the radiator halves are arranged closer to the base than the metal strips. Seen in plan view, the metal strips are arranged on the dipole-shaped antenna element arrangement in the region of the outer sides of the radiator halves. The metal strips are preferably rectangular structures.
A metal strip of this type extends, in each case, approximately in parallel with in each case two outer sides of two adjacent radiator halves. In this case, the two radiator halves belong to different pairs of radiator halves. Particularly good results are achieved if each metal strip extends in parallel with a frame side of the frame web. Preferably, each metal strip is arranged in such a way that it does not overlap with a recess which is situated within the radiator halves and is defined by each radiator half. The metal strips act as parasitically coupled resonators. In this case, the height of the resonators above the dipole is less than when using a director. As a result, the dipole-shaped antenna element arrangement can be more compactly constructed and also placed in smaller radomes.
In another embodiment, the metal strips are arranged further away from a longitudinal axis penetrating the centre of the antenna element arrangement than the respective outer sides of the radiator halves.
In a further embodiment, preferably at least four metal strips are used. In each case one of the metal strips is arranged in the region of the outer sides of in each case two adjacent radiator halves. In this case, two adjacent metal strips preferably extend at an angle of approximately 90° to one another in each case, whereby said strips end at a distance from one another.
In an additional embodiment of the dipole-shaped antenna element arrangement, a plurality of possibilities are disclosed as to how the metal strips can be arranged in comparison with the two outer sides of two adjacent radiator halves. For example, it is possible, in a plan view of the dipole-shaped antenna element arrangement, for at least part of the width of the at least one metal strip to overlap the two outer sides of the two adjacent radiator halves. In this case, preferably, the area of the metal strip which overlaps the first radiator half is approximately as large as the area of the metal strip which overlaps the second radiator half. Alternatively, it is also possible for the at least one metal strip to directly abut two outer sides of two adjacent radiator halves without any overlap taking place. In this case, an imaginary plane extending through the side walls of the outer sides of the adjacent radiator halves and through the outer side of the metal strip would lie perpendicularly to the radiator plane. Furthermore, it is alternatively possible for the at least one metal strip to be arranged so as to be offset relative to the two outer sides of the two adjacent radiator halves without overlap in such a way that, in a plan view, a gap is also formed between the metal strip and the two adjacent radiator halves. In this case, the metal strip extends further outwards than the two outer sides of the radiator halves.
Preferably, the length of the metal strips corresponds approximately to a quarter of the wavelength of the centre frequency.
In another embodiment, the passive beam-shaping frame is held, together with the director or the metal strips, galvanically separated via at least one combined holding and spacing element, supported on one or all of the radiator halves and at a distance therefrom. By this means, the assembly can be significantly simplified.